The present invention relates to the preparation of unsaturated nitriles utilizing olefin starting materials, and more particularly, to the vapor phase ammoxidation of propylene or of isobutene, respectively, to produce acrylonitrile or methacrylonitrile in the presence of catalysts having a base of antimony and of tin.
There are a number of patents, particularly French Pat. Nos. 1,299,139 and 1,293,088, which show catalysts based on the oxides of antimony and on the oxides of tin. Such catalysts enable the preparation of unsaturated nitriles starting with olefins. It has also been shown in other patents, particularly in Certificate of Addition 81,246 to French Pat. No. 1,299,139 and in French Pat. Nos. 2,176,770 and 2,176,139 that the oxides of polyvalent metals such as iron, copper, vanadium, titanium, calcium, and barium are able to be advantageously used in combination with the oxides of antimony and of tin to oxidize propylene in the presence of ammonia to obtain acrylonitrile.
Other combinations of polyvalent metal oxides with the oxides of antimony and of tin have been shown in a very general fashion in such patents as French Pat. Nos. 2,020,512 and 2,065,317 and in British Pat. No. 1,280,073. Certain of these combinations, and particularly those of French Pat. No. 2,176,771, increase the conversion rate of propylene to acrylonitrile, but this requires relatively long contact times so that the productivity is insufficient for industrial usage.